First you have to install Postgres.app and Ruby on your computer. Then download this template, cd to it, and install the gems
$ bundle install
To run the app locally, install Shotgun and run
$ shotgun config.ru
Your app should then be running at http://localhost:9393.
Heroku relies on Git for deploying apps so initialize git for the app.
$ git init
$ git add .
$ git commit -m "Initial Commit"
To create a Heroku app, first be sure you are signed up. Then type the following in Terminal while inside of the project directory.
$ heroku create NAME_OF_YOUR_APP
Once this returns successfully, push your app to Heroku.
$ git push heroku master
If you're using DataMapper with a database, you will need to add a database. Run these commands from the root of your project, relacing the last database url with the name logged after the first command.
$ heroku addons:add heroku-postgresql:dev
$ heroku pg:promote [HEROKU_POSTGRESQL_REPLACEME_URL]
Now you've created your database. Now you need to update the tables:
$ heroku run console
$ require './app.rb'
$ DataMapper.auto_upgrade!
$ exit